The Science of Crawling

My daughter does not get around like other babies. Shortly after learning to sit, she developed a mode of transport nothing like the traditional crawl: she slides around the room on her bum, using one foot as an anchor and an arm to steer — something like a monkey carrying a banana in one hand. It looks funny, but it sure does get her from point A to point B.

It didn’t occur to me that I should worry. The scoot was creative. My daughter was an early and strong sitter — perched sturdy around five months and content to sit and play while other babies lounged on their backs or tummies, so getting around while sitting up seemed logical. When we visited friends or she chugged around on the grass at the park, someone would inevitably relate and tell me that their son or daughter had done something similar as a baby.

But when she passed her first birthday, still shuffling and showing no signs of getting on her hands and knees like the others (or pulling to stand), I decided to investigate. I called a therapy center on the west side of Los Angeles and went in for an assessment.

Sure enough, there was work to be done. Immediately, the occupational therapist could see that she favored one leg, and her strength and muscle development was uneven (the leg she pushed in front was weaker). I was curious about the goal, though. Should we teach her to crawl? I’d heard it was good for the brain. If she skipped this phase and went straight to walking, would she miss out on an important neural exercise?

It’s a long-standing belief that crawling is important. Moving on all fours and organizing the right and left sides of the body has been thought to strengthen connections between the two hemispheres of the brain, and even lay the foundation for later skills like hand-eye coordination. Though I’d heard this idea casually through friends and teachers, I’d never looked into it more closely.

When I did, crawling wisdom turned out to be largely unfounded. The limited research on the topic of crawling shows that those who do it are no different than those who skip this stage. Babies have been either hitting this motor milestone a little later on average or breezing over it since the 1990s, when the Back to Sleep campaign started — presumably because less tummy time makes for less practice on all fours. Studies indicate this is all without negative repercussion, though. For example, a large study of babies born before and after back-sleeping became the norm found that more back-sleepers crawled later or not at all in comparison to tummy sleepers, but that at 18 months of age all were equal on measures of social, communication, fine and gross motor development. Another study found that back sleepers trailed stomach sleepers in early motor development, but that differences washed out by the time they walked. In this study, 30 percent of babies skipped crawling altogether — without a problem later on.

In fact, anthropologists have argued that crawling is a relatively recent human activity (meaning it couldn’t well be critical to development). In traditional cultures parents carry their little ones; for example, moms in Papua New Guinea tote babies 86 percent of the time until their first birthday, and then send them right on to moving upright, never bothering with the ground, or “tummy time.” In fact, these researchers propose crawling wouldn’t be evolutionarily adaptive, since it means hands always in the dirt. Better to wait until babies can stand until you put them down.

So, crawling is optional.

But at my daughter’s therapy sessions, the goal is not to crawl. It’s to help her movement and muscles develop evenly and in a coordinated way. In our first session, Melissa Edelstein, director of the Child Success Center, explained, “Often if a skill (such as crawling) is not developed, it’s because the underlying motor patterns or another foundational skill are not present.” Motor patterns are the sequences of movements that make up a particular skill. It’s not always clear why they develop irregularly for some babies — in my daughter’s case, her strength could have been uneven, or her brain signaled her muscles to make this awkward movement. Either way, it wasn’t serving her very well. At 13 months, she didn’t plant her right foot on the floor or pull to stand and bear weight on that foot, and the more she compensated with her off-kilter crawl, the greater the difference became.

“Many of the higher-level motor and academic skills are built from these early milestones,” she explained. “For example, we often see children who have skipped or have delayed milestones as being clumsy and uncoordinated.” Even if crawling isn’t necessary, I can see how this applies to my daughter. Babies who crawl in the traditional way (or skip it and go straight to walking) give equal input to both sides of the body, whereas my daughter was going on five months of a lopsided workout. I’m a dancer, so my ears perked up, imagining her later in life with a skewed center and wobbly pirouettes.

In the end, I’m glad we got help. I don’t fret over her development or her future chances at Lincoln Center; my daughter’s a beautiful talking, social, and dexterous little being — but I’m happy we nudged her onto a more balanced path of motor abilities. One of the most helpful parts of her therapy has been to watch the clinician and replicate the exercises at home. Within a week of starting therapy, my daughter bore weight on both feet, squatted evenly, and pulled herself up. A week after that, she spent half her time upright, reaching for formerly off-limits household objects. Even if it helps just a bit later on, it was worth it. Now she’ll figure out walking on her own timeline — even if she gets a few confused looks at the park while she’s shuffling around and working on it.

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